The present invention relates to a procedure for controlling an elevator group, as defined in the preamble of claim 1.
When a number of elevators form an elevator group that serves passengers arriving in the same lobby, the elevators are controlled by a common group controller. The group control system determines which elevator will serve a given landing call waiting to be served. The practical implementation of group control depends on how many elevators the group comprises and how the effects of different factors are weighted. Group control can be designed to optimise cost functions, which include considering e.g. the passenger waiting time, the number of departures of the elevators, the passenger ride time, the passenger journey time or combinations of these with different weighting of the various factors. The group control also defines the type of control policy to be followed by the elevator group.
Additional features will be added to group control when the elevators are double-deckers, where two decks are attached on top of each other in a frame and the elevator serves two building floors simultaneously when the elevator stops.
A conventional control solution is based on collective control, in which the elevator always stops to serve the nearest landing call in the drive direction. If the call is allocated to the trailing car, coincidences with possible landing calls from the next floor are maxinised. Collective control in elevators with normal cars is ineffective in outgoing and mixed traffic. The consequence is bunching and bad service for the lowest floors. The same applies to collective control of double-deck elevators. For example, specification U.S. Pat. No. 4,632,224 presents a collective control system for double-deck elevators in which a landing call is allocated to the trailing car in the travelling direction of the elevator, in other words, when the elevator is moving down, the landing call is allocated to the upper deck, and when the elevator is moving up, the landing call is allocated to the lower deck. Another specification U.S. Pat. No. 4,582,173 discloses a group control for a double deck elevator calculating internal costs corresponding to the waiting times inside the car during the stops and external costs corresponding to the waiting times on the landing call floors. In this control only the operating costs consisting of these time losses of the passengers are minimised.
The object of the invention is to achieve a new procedure for controlling an elevator group in order to improve passenger journey times, i.e. the total time spent in an elevator system and to allow better utilisation of the capacity of the elevator group. To implement this, the invention is characterised by the features presented in the characterisation part of claim 1.
Certain other embodiments of the invention are characterised by the features presented in the characterisation parts of the sub-claims. According to one feature if the invention the journey time consisting of waiting time at the landing call floor and ride time inside a car to the destination floor, is optimised by minimising the passenger waiting time and ride time. Especially the journey time is optimised so that a landing call for an elevator comprising two decks is selected by minimising the passenger waiting time and the best deck to serve the landing call is selected by minimising the passenger journey time.
In a preferred application of the invention the passenger waiting time is optimised by minimising a waiting time forecast WTFetc, which comprises the current landing call time weighted by the number of persons waiting behind the call and the estimated time of arrival of a car to the landing call. All the passengers waiting the serving car is in this modification taken into account.
In another modification of the invention the passenger journey time is minimised by allocating the landing call to the deck that will cause the fewest additional stops to the elevator and least additional delay on the way to the passenger destination floor. Also the passenger ride comfort increases as the number of stops decreases.
In a further embodiment of the invention the elevator estimated time of arrival ETA to the destination floor is calculated separately for each deck, taking into account the stops already existing for the elevator and the additional stops caused by the selected landing call, and the landing call is allocated to the deck for which the estimated time of arrival to the destination floor is smallest.
In a preferred modification of the invention the best deck for each landing call is selected by minimising the cost function. The cost function may comprise the estimated time of arrival ETAd to the destination floor. Alternatively, the cost function may also comprise the estimated time of arrival ETAf to the furthest call floor.
Advantageously, when calculating the ETA, the future stops and stop times are based on the existing car calls and landing call stops and on the additional stops and delays caused by the call to be selected. The additional delays caused by the landing call to be selected are obtained from the statistical forecasts of passenger traffic, which includes passenger arrival and exit rates at each floors at each time of the day.
The solution of the invention allows a substantial increase in the capacity of an elevator group consisting of double-deck elevators as compared with solutions based on collective control. In the solution of the invention, passenger service is taken into consideration. Shorter journey and elevator round trip times are achieved which increases the handling capacity. The level of service to passengers is also substantially improved.
The optimisation of passenger waiting times the invention has been compared with a prior-art method in which only the call times are optimised. Passenger waiting time starts when a passenger arrives to a lobby and ends when he enters a car. Call time starts when the passenger pushes a call button and ends when the landing call is cancelled. These times are different especially during heavy traffic intensity. Number of passengers is obtained from the statistical forecasts. The average waiting times for outgoing traffic especially in heavy traffic conditions were clearly shorter. As for waiting times of each floor, the average waiting times are shorter and better balanced at different floors, especially at the busiest floors. The control procedure keeps the elevators apart from each other, evenly spaced in different parts of the building. The best car to serve a landing call is so selected that coincident calls, i.e. car calls and allocated landing calls, will be taken into account.
The average and maximum call times are also reduced. The invention produces effective service and short waiting times especially during lunch-time traffic and in buildings having several entrance floors, which is difficult to achieve with conventional control procedures.